1. Field of the Invention
The present invention relates to a transmission for a vehicle, and more particularly, to a technology for a transmission structure that can overcome a torque interruption phenomenon during gear shift while utilizing a synchronized gear type transmission mechanism.
2. Description of Related Art
A main problem in development of transmissions mounted to vehicles is to reduce the number of parts of a transmission, the weight, overall length, and volume of the transmission.
The volume of the transmission influences a mounting performance of the transmission to a vehicle, and the weight of the transmission is a factor that greatly influences a fuel ratio of the vehicle.
Meanwhile, the basic form of the present invention is a synchronized gear type transmission mechanism in which two transmission gears are engaged with each other to circumscribe each other and configured to transmit power through one of the transmission gears selected by a synchronizing unit.
The above-described synchronized gear type transmission essentially generates a torque interrupting phenomenon by which transmission of power is interrupted while a synchronizing unit is released from the previous gear shift and is coupled to a gear shift that will transmit power newly, which is a main cause of lowering a gear shift feeling. The lowering of the gear shift feeling due to the cause becomes a big problem in lower stages such as first to third stages but a driver tends to feel the phenomenon relatively less at a high speed.
FIG. 1 is a view showing a structure of a transmission that has been studied to overcome a disadvantage of a conventional synchronized gear type transmission. The transmission includes a first input shaft 500 for always receiving power from an engine, and a second input shaft 504 that is a hollow shaft surrounding an outer side of the first input shaft 500 such that the power of the engine can be transmitted through a first clutch 502. A second stage driving gear 506 is disposed in the first input shaft 500 to receive power through the second clutch 508, and the first, third, fourth, fifth, and sixth driving gears other than the second stage driving gear are disposed in the second input shaft 504. Thus, if the second clutch 508 is coupled while releasing the first clutch 502 when shifting a gear to the first stage and the second stage, the gear shift to the second stage can be performed without causing a torque interruption phenomenon, and if the first clutch 502 is coupled while releasing the second clutch 508 in a state in which the third stage synchronizing unit is coupled in advance even during the gear shift to the second stage and the third stage, a torque interruption phenomenon can be excluded.
For reference, FIG. 1 shows a flow of power through which a first stage output is formed in the transmission by a dotted arrow and shows a flow of power through which an R stage output is formed by a solid line.
However, in the transmission having the above-described structure, the second input shaft 504, including the first stage driving gear 510, is a hollow shaft and a diameter of the second input shaft 504 should be enlarged to a predetermined level to secure strength of the first stage driving gear 510. If the diameter of the first stage driving gear 510 becomes enlarged, both the diameter of the first stage driven gear 512 engaged with the first driving gear 510 and the distance between the first stage driven gear 512 and the first driving gear 510 should become enlarged to realize a desired first stage gear shift ratio, which causes the weight and volume of the transmission to increase significantly.
For reference, reference numeral 512 denotes a differential gear for distributing power to two driving wheels, reference numeral 516 denotes a first output shaft, reference numeral 518 denotes a second output shaft, and reference numeral 520 denotes a reverse idler shaft.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.